The electrode of a plasma cutting torch, in particular a manual torch, is usually taken to high voltages while it is in use, often more than 100 V and sometimes up to 300 V.
While the torch is operating, the electrode is normally rendered inaccessible to the operator due to the presence of the nozzle of the torch which is positioned around the electrode in a way which is known in itself.
However, when it is necessary to dismantle the nozzle, for example during a maintenance operation on the torch, the electrode is then exposed, that is to say accessible to the operator.
This configuration now presents a real danger for the operator, who risks being electrocuted in the event of involuntary actuation of the control trigger of the torch.
In order to limit the risk for the operator, it is then appropriate either to prevent access to the pieces which are live when the torch is dismantled, or to prevent the current generator operating if certain pieces of the torch are not in place.
To do this, safety devices have already been proposed in the prior art, but these afford only a partial response to the abovementioned problem.
Thus the document EP-A-110736 proposes a safety system based on a check of the presence only of an insulating protective skirt arranged around the nozzle of the torch.
In other words, this system does not take into account the presence of the nozzle, and an operator who is distracted may refit this protective skirt while omitting to replace the nozzle, which would enable access to the electrode by the operator and would thus be likely to expose the latter to a significant risk of electrocution by contact with the live pieces, especially the electrode.
Other safety systems have, moreover, been proposed by the documents DE-A-4313830, GB-A-2192821, FR-A-275270, JP-A-01057982, FR-A-2450659, US-A-3,488,466 and US-A-3,632,951. However, these known configurations still do not give complete satisfaction, especially due to the difficulty of implementation, their inadequate safety level and/or their high cost of manufacture.
Moreover, the document DE-A-3714995 describes a plasma torch equipped with a nozzle about which a protective shroud is arranged comprising a safety system comprising an electrical switch capable of being actuated by a moveable push rod in elongate form, this push rod being formed in a housing situated within the torch body. According to this document, the push rod interacts with the nozzle by means of a moveable annular component. Moreover, the protective shroud is mounted on the body of the torch.